The Panasonic FZ 200 with a maximum aperture of F2.8 across the entire zoom range looks as though it could be a lightweight substitute for an APS-C or DX format DSLR used with the Canon 100-400 IS or Nikkor 80-400 VR. These lenses are relatively light because their maximum aperture at the long end is only F5.6, but they are a heck of a lot heavier than the Panasonic FZ 200. A slight compromise in image quality could be worth the huge savings in weight and cost.

I'm trying to get an idea of the degree of loss of image quality, comparing images from a D7000, for example, with 400mm lens used at F8, and camera set at ISO 800 for a fast shutter speed, as opposed to the FZ-200 at ISO 100 and F2.8 which would allow the same shutter speed.

Theoretically, the Nikon D7000 at ISO 800 should produce similar image quality to the FZ 150 or FZ 200 at ISO 100. SNR, DR and Tonal Range etc should be similar, according to DXOMark. The D7000 might have the edge because of its greater pixel count, but not in any significant way, I believe.

My main concern would be the quality of that Leica lens at full aperture. Most lenses are not sharpest at full aperture. One usually needs to stop down at least one stop. Both the Canon and Nikon 400mm zooms tend to be sharpest at F8, at 400mm, although there obviously are QC variations so it might be the case that some folks have a copy of one of these models which is sharpest at F5.6, or equally as sharp at F5.6 as at F8.

Of course, it's understood that the DSLR will always produce better image quality when shutter speed is not an issue. The main attraction for me is a 600/F2.8 lens which weighs less than 600gms including camera body.

Does anyone have any links to preview images from the FZ200 which show a comparison between F2.8 and F4 sharpness? Has anyone compared images from the FZ150 at ISO 100 with the same scenes shot with a Nikon DX at ISO 400 or 800?

Also significant is the effectiveness of the optical image stabilizer in the Panasonic models. Those Canon and Nikon 400mm zooms have very ancient IS or VR systems. If the nore modern IS systems of the F150 and F200 provide just one stop greater advantage than the old Canon and Nikon lenses, we might have a situation whereby the Panasonic provides equal image quality at half the shutter speed, or perhaps even better image quality at equal shutter speeds (eg. comparing ISO 100 with ISO 1600).

Anyone got any thoughts on this, or links to comparison RAW images? I always shoot in RAW mode.